Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
  • H04R1/00—Details of transducers, loudspeakers or microphones
  • H04R1/20—Arrangements for obtaining desired frequency or directional characteristics
  • H04R1/22—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired frequency characteristic only 
  • H04R1/28—Transducer mountings or enclosures modified by provision of mechanical or acoustic impedances, e.g. resonator, damping means
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
  • H04R1/00—Details of transducers, loudspeakers or microphones
  • H04R1/20—Arrangements for obtaining desired frequency or directional characteristics
  • H04R1/22—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired frequency characteristic only 
  • H04R1/28—Transducer mountings or enclosures modified by provision of mechanical or acoustic impedances, e.g. resonator, damping means
  • H04R1/2803—Transducer mountings or enclosures modified by provision of mechanical or acoustic impedances, e.g. resonator, damping means for loudspeaker transducers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
  • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
  • B01J20/10—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising silica or silicate
  • B01J20/16—Alumino-silicates
  • B01J20/18—Synthetic zeolitic molecular sieves
  • B01J20/183—Physical conditioning without chemical treatment, e.g. drying, granulating, coating, irradiation
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
  • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
  • B01J20/10—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising silica or silicate
  • B01J20/16—Alumino-silicates
  • B01J20/18—Synthetic zeolitic molecular sieves
  • B01J20/186—Chemical treatments in view of modifying the properties of the sieve, e.g. increasing the stability or the activity, also decreasing the activity
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
  • H04R1/00—Details of transducers, loudspeakers or microphones
  • H04R1/02—Casings; Cabinets ; Supports therefor; Mountings therein
  • H04R1/025—Arrangements for fixing loudspeaker transducers, e.g. in a box, furniture

Definitions

• This disclosure relates to a loudspeaker system.
• One goal of loudspeaker systems is to achieve a low resonant frequency in a speaker enclosure that has a relatively small internal volume.
• the resonant frequency of a speaker enclosure can be decreased by adding an air adsorber to the enclosure; the adsorber acts to increase air compliance of the enclosure.
• a good adsorption material should have at least the following characteristics.
• the amount of gas adsorbed and desorbed should be strongly dependent on the pressure change. Also, the adsorption properties of the material should not degrade or change significantly when exposed to different environmental conditions.
• Moisture in the atmosphere is one of the key elements detrimental to the proper function of adsorption materials. Often when an adsorption material is exposed to a humid environment many adsorption sites are preferentially occupied by water molecules, leaving few sites for the adsorption/desorption of air molecules. This phenomenon renders the adsorption material ineffective in regulating the pressure of an acoustic enclosure through adsorption/desorption of air inside the enclosure.
• Zeolites are silicates that tend to adsorb water vapor from the environment; some zeolites are even used as drying agents. Many zeolites will also adsorb and desorb air from the atmosphere. The adsorption behavior of zeolite depends on both the structure and composition. Aluminum is commonly present in silicate zeolites. Since aluminum has a different oxidation state than silicon (Al is +3 and Si is +4), its presence creates local polar sites. And, since water vapor is polar, zeolites with aluminum tend to preferentially adsorb water vapor over air. Water vapor adsorption decreases the ability of zeolites to adsorb air and accordingly decreases their ability to enhance the acoustic compliance of loudspeaker enclosures.
• This disclosure relates to the use of an air adsorbent that is effective to increase the air compliance of a loudspeaker enclosure.
• the adsorbency is minimally degraded by the presence of humidity.
• a loudspeaker system that uses the adsorbent thus exhibits long-term increased air compliance without the need to use high-purity adsorbent material or install a cumbersome humidity control system in the speaker enclosure.
• the adsorbent is a silicate zeolite that is made with a moderate amount of aluminum: typically the zeolite has a Si/Al mole ratio of from at least about 200 to less than 400.
• the silicon source material used to produced such zeolites can be less pure than that required by the highly pure silicate zeolites with Si/Al mole ratios of 400 or greater. The result is a relatively inexpensive loudspeaker enclosure with increased compliance and thus a lower resonant frequency.
• zeolite When zeolite includes elements such as aluminum that have a different oxidation state than silicon, the zeolite will bind with counter ions to achieve charge neutrality. Commonly these counter ions are cations such as hydrogen ions. The greater the amount of aluminum in the zeolite, the greater the number of such counter cations.
• hydrogen ions When hydrogen ions are present as counter cations, when the zeolite is exposed to water or moisture the water will become acidic; acidic moisture will corrode many metals. The zeolites with this behavior are termed "acidic zeolites" here. Using acidic zeolites in an enclosure can cause corrosion problems in structures such as loudspeaker enclosures that have metal parts.
• the acidity of silicate zeolites with a second metal such as aluminum can be controlled by judicious choice of counter cations that are not acidic, such as ammonium, alkali metals, alkaline earth metal ions, and metal ions. If the material is too acidic a process such as ion exchange can be employed to reduce the amount of hydrogen ions and replace them with alkaline ions such as ammonium.
• a process such as ion exchange can be employed to reduce the amount of hydrogen ions and replace them with alkaline ions such as ammonium.
• One example of the loudspeaker system includes an enclosure, an electro-acoustic transducer mounted in the enclosure so as to leave space inside of the enclosure that is unoccupied by the transducer, and an air-adsorbing material in the space inside of the enclosure that is unoccupied by the transducer.
• the air-adsorbing material can be a silicon-based zeolite that includes a small amount of a second metal, wherein the mole ratio of silicon to the second metal is at least about 200 and is less than 400.
• the zeolite can have a molecular structure of the MFI, FER or MEL type.
• the air-adsorbing material can include one or more types of zeolite. In one non-limiting example, the air-adsorbing material consists entirely of the zeolite.
• the second metal may be primarily or exclusively aluminum.
• the second metal may be selected from the group of elements consisting of B, Al, Ti, Ge, Fe, Ga and the rare earth elements.
• the zeolite may be in powder form.
• the zeolite may be configured such that, as compared to the dry state, when exposed to conditions of at least about 90% relative humidity at 40°C over a period of time until weight gain due to water adsorption is essentially stabilized, the apparent volume ratio achieved with the zeolite measured at 100 Hz decreases by no more than about 10%, and more specifically may be in the range of from about 3% to about 10%.
• the air adsorbing material may include counter cations to balance charges of the zeolite due to the presence of the second metal or metalloid.
• the counter cations may include relatively few hydrogen ions.
• the counter cations may be selected such that when one part zeolite is mixed with five parts water the pH remains above 4.
• the air adsorbing material may exhibit an equilibrium water weight gain of less than about 10%, and more preferably may be less than about 7%.
• Another example includes a loudspeaker system with an enclosure, an electro-acoustic transducer mounted in the enclosure so as to leave space inside of the enclosure that is unoccupied by the transducer, and an air-adsorbing material in the space inside of the enclosure that is unoccupied by the transducer; the air-adsorbing material comprises a silicon-based zeolite with sufficiently few hydrogen ion counter cations such that when one part zeolite is mixed with five parts water the pH remains above 4.
• the zeolite may include a small amount of a second metal, wherein the mole ratio of silicon to the second metal is at least about 200 and is less than 400.
• the second metal may be primarily or exclusively aluminum.
• the zeolite may have a molecular structure of the MFI, FER or MEL type.
• the apparent volume ratio achieved with the zeolite measured at 100 Hz may decrease by no more than about 10%, and more preferably may decrease by from about 3% to about 10%.
• FIG. 1 Another example includes a loudspeaker system having an enclosure, an electro- acoustic transducer mounted in the enclosure so as to leave space inside of the enclosure that is unoccupied by the transducer, and an air-adsorbing material in the space inside of the enclosure that is unoccupied by the transducer.
• the air-adsorbing material comprises a silicon-based zeolite that has a molecular structure of the MFI, FER or MEL type and that includes a small amount of aluminum, wherein the mole ratio of silicon to aluminum is at least about 200 and is less than 400.
• the air adsorbing material further comprises counter cations to balance charges of the zeolite due to the presence of the aluminum, wherein the counter cations are selected such that when one part zeolite is mixed with five parts water the pH remains above 4.
• the apparent volume ratio achieved with the zeolite measured at 100 Hz decreases by from about 3% to about 10%.
• the air adsorbing material exhibits an equilibrium water weight gain of less than about 7% under the subject conditions.
• Figure 1 is a schematic diagram of a loudspeaker system of the present disclosure.
• Figure 2 is a plot of the reduction of apparent volume ratio as a function of steady state water vapor uptake for various zeolite adsorbents.
• Loudspeaker system 10 includes enclosure 12. Electro-acoustic transducer 14 is mounted in enclosure 12 so as to project sound from the enclosure while leaving space 16 inside of enclosure 12 that is unoccupied by transducer 14. Air-adsorbing material 18 is located in space or volume 16 inside of enclosure 12 that is unoccupied by transducer 14. Enclosure 12 can be closed, or it can be partially open, e.g., as would be accomplished with one or more ports (not shown).
• Material 18 may be a silicon-based zeolite that includes one or more second elements (typically metals or metalloids) such as B, Al, Ti, Ge, Fe, Ga, or a rare earth element in the framework. In one non-limiting example, the mole ratio of silicon to the second element(s) is at least about 200 and is less than 400. Material 18 can consist entirely of zeolite, or zeolite can make up only part of the material. Further, one or more types of zeolite can be included in the zeolite component of material 18. The amount of air absorbing material used in the speaker enclosure and its particle size can be varied, according to need. For example, the material can be present as an un-agglomerated powder, an agglomerated powder, or other forms, shapes and sizes. Generally, more adsorbent in the speaker enclosure leads to greater compliance.
• second elements typically metals or metalloids
• the mole ratio of silicon to the second element(s) is at least about 200 and is less than 400.
• Material 18 can consist entirely
• the cost, weight and volume of the adsorbent are practical factors to be considered. Also, the adsorbent powder should not be packed so tightly as to affect the ability of air molecules to freely adsorb/desorb from the adsorbent.
• the air-adsorbing material is preferably a silicon-based zeolite which includes a relatively small amount of one or more additional metals or metalloids; in one case the second metal is aluminum.
• Zeolites can exist in myriad types of crystal structures, any or all of which may be appropriate for the air adsorbent herein. Types of zeolites that have been shown to be appropriate air adsorbent materials for the subject loudspeaker system include MFI, MEL and FER-type zeolites, where MFI, MEL, and FER are framework code types assigned by the International Zeolite Association.
• One way to minimize the sites of alumino-silicate zeolites to which water vapor will readily bind is to increase the Si02/A12O3 ratio. Since aluminum is a common impurity in the silica source material used in synthesis of zeolites, to achieve high Si02/A1203 molar ratio expensive, difficult to source high-purity silica source material is required, and there needs to be strict control of zeolite synthesis so as to minimize Al contamination.
• the data presented herein helps to establish that for zeolites with a mole ratio of Si to Al of from at least about 200 up to less than 400, the material provides acoustic performance benefit without the need to use high- purity silica source material or to control synthesis conditions as strictly as is necessary to achieve Si:Al mole ratios of 400 or greater.
• the result is a material that can be readily used in commercial loudspeaker systems.
• the subject zeolite has a mole ratio of silicon to the second element in the range of from at least about 200, up to less than 400, it is able to retain up to about 90% of its air absorbency even after extended exposure to high humidity, indicating that the nitrogen binding sites of the zeolite material are not substantially affected by water molecules.
• Air compliance is calculated as cone displacement* cone area/pressure.
• the "apparent volume ratio” equals the air compliance with adsorbent divided by the air compliance without adsorbent; data is set forth in the Table 1 below
• Figure 2 is a plot of the reduction in apparent volume ratio (from dry to equilibrated state after exposure to 40°C, 90% relative humidity conditions until the weight gain is essentially stabilized) as a function of steady state water vapor uptake for several zeolite adsorbents.
• activated carbon is a common adsorbent
• Table 2 compares the (apparent) volume ratio of an acoustic box containing an MFI silicate zeolite (zeolite 6 in Table 1) to that of BPL 6x16 mesh activated carbon from Calgon, in both the dry state and when equilibrated to 40°C, 90% RH.
• the loading of adsorbents in the loudspeaker box was about 35-40 volume %.
• the performance was compared at 10Hz.
• the activated carbon is shown to be essentially ineffective at increasing compliance, while the zeolite has only about a 5% decay in performance, even though the exposure time of Zeolite to the humid environment is much longer.
• the zeolite When the second elements in the silicate zeolite are of different valance from silicon, the zeolite will not be neutrally charged and so will contain charged counter ions such as alkali metals, ammonium, hydrogen ions, metal ions, or mixtures thereof that act to balance the charge of the zeolite.
• the counter ion influences the acidity of zeolite.
• the acidity of zeolite was determined by mixing one part zeolite to five parts of water and measuring the resulting pH. It is desirable to use a zeolite with a pH greater than 4 as measured in this manner, so as to reduce any tendency of the zeolite to corrode metal inside the speaker enclosure.
• zeolite 6 (Tables 1 and 2) includes ammonium counter cations and its pH is 7.
• the counter cations in this same zeolite become hydrogen ions if the material is heat treated in air at 600°C, and in turn the pH of this zeolite decreases to 3.2. It has been determined that potential corrosion caused by such acidic zeolites is decreased when its pH, as measured per the above procedure, is above 4.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Inorganic Chemistry (AREA)
• Analytical Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Acoustics & Sound (AREA)
• Signal Processing (AREA)
• Otolaryngology (AREA)
• Health & Medical Sciences (AREA)
• Details Of Audible-Bandwidth Transducers (AREA)
• Silicates, Zeolites, And Molecular Sieves (AREA)
• Solid-Sorbent Or Filter-Aiding Compositions (AREA)

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• 2012
  • 2012-08-31 US US13/600,941 patent/US8687836B2/en active Active
• 2013
  • 2013-08-29 WO PCT/US2013/057333 patent/WO2014036289A1/en active Application Filing
  • 2013-08-29 EP EP13759413.1A patent/EP2890491A1/de not_active Withdrawn
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